Re: NTSC Flat C-128 IEC serial problem

From: gsteemso <48bitsorbust_at_gmail.com>
Date: Fri, 3 Sep 2021 22:01:44 -0700
Message-Id: <B4DCF463-B3EB-44FB-B77A-2707337672F6_at_gmail.com>
I'm looking at what you've done so far and, without actually opening up one of my own machines to compare, it certainly _sounds_ like you've covered all the bases on the hardware side.

However, the hardware is driven by software. (well, firmware unless you type in a test routine...) Have you checked the ROMs? A quick test would be to see if you get the same issue in 64 mode; it has a completely independent ROM set. If there's a smidgen of bit rot in one ROM, it's unlikely to also be present in the other set.

G.

> On Sep 3, 2021, at 9:46 AM, Terry Raymond <traymond160_at_gmail.com> wrote:
> 
> 
> Hi all,
> 
> Years ago I bought an NTSC Flat C-128 off ebay it powers up just fine but it has this issue and error with the IEC when any DOS command is issued in basic:
> 
> DEVICE NOT PRESENT ERROR?
> 
> I cleaned the userport edge connectors
> and the cartridge port connectors  they seemed to be corroded and dirty.
> 
> Just last fall I bought a new C64/C128 Diagnostic harness out of Canada
> so i hooked that up but had an issue with the keyboard dongle and Im sure I plugged that in the right way, but when I powered the C128 on it went straight into the Monitor.
> So I just didnt plug in the keyboard dongle and then the Diagnostic would start.
> So I tested the following:
> 
> 1-CIA that handles the IEC serial work---Tested okay and I have working CIA spares.
> 
> 2- TTL chip that works inline with the CIA--- desoldered and replaced IC, no difference same IEC serial error.
> 
> 3- Diodes in all of the IEC circuit---- Replaced--- Result same serial error.
> 
> 4- Replaced DIN serial socket-- I admit I messed up 2 traces so I added bodge wires, and I tested the continuity with a Multi meter and all seem okay then.
> 
> So with all of that still the same Device Not Present Error? comes up.
>  Yeah all of my disk drives work fine with all my other Commodore computers.
> 
>   Would both the 8502 processor or the PLA be a culprit but they didnt test faulty in the
> Diagnostic?
> 
>   Suggestions appreciated I just dont know what else to do as I stated the
> Diagnostic cartridge says all other chips are OK and I have run that dozens of times with the same test results so Im really stumped.
> 
> The Diagnostic harness is awesome it did point me in the right directions and I love these tools so theres no guess work, kind of when it still leaves you with nothing to find is what is puzzling so just the experience of just what to look for is what I dont have I admit.
> 
> Terry Raymond
> 
> 
> 
> 
> 
Received on 2021-09-04 08:00:02

Archive generated by hypermail 2.3.0.